Purification of arsenical sulfuric acid.



I PATENTBD AUG. 20, 1907. J. RASGHEN, A. E. WAREING & J. H. snows. EURIFIGATION 0P ARSBNIGAL SULFURIG ACID.

APPLICATION FILED MAE. 21,1906.

2 SKEET8-SHBBT 1.

mvemorzs'.

WIINPESSES 71/5 A fdi M ATTORNEYS APPLIOATIOI FILED IAB. 21,1908.

2 sums-sum 2.

INVENTORS I WITNESSES Zia ATTORNEYS chlorid, the said sulfuric acid passing away in a purified Be it known that we, JULIUs RAsOnEN, a subject of condition, the arsenious ch1orid thus blown from the the King Of Great Britain and Ireland, Ph. D., analytsulfmic acid passing into ascrubbing tower down which ical chemist, ARTHUR EDWARD WAREING, a subject of water is caused to flow (and which can be made to circu- 5 the King of Great Britain and Ireland, chemist, and late if desired) so that decomposition takes place be- JEFF HENRY SHORES, a subject of the King oi Great tween the. arseniouschlorid and water with the forma- Britain and Ireland, M. Sc, Ph. D., analytical chemist, tion of arsenious' oxid and hydrochloric acid, which all residing at 3O James street, Liverpool, in the county arsenious oxid is however contaminated with traces of of Lancaster, England, have invented new and useful seleniu1n. To this mixture SLlillClQIlt arsenious chlorid,

1U Improvements in the Purification of Arsenical Sulfuric which had previously separated as an oily liquid from 6b Acid and the Obtainment of Arsenic Therefrom, of the sulfuric acid, is added to redissolve the whole of the which the following is a specification. precipitated arsenious Oxid, when, on the addition of a The object of this invention to provide an eflicient little water, it will be found that the selenium is pre and economical process, by which 'arsenical sulfuric cipitated. The whole mixture is then filtered so as to 15 acid can be purified and obtained in a practically pure separate the selenium and water is added to the clear condition and bywhich whitearsenic is obtained thereliquid, to make the density of the solution equal to from which is also practically pure without distillation about 28 Twaddle, when a considerable quantity (say being necessary. seventy per cent.) of the arsenic is precipitated asarse- This invention is especially intended for the treatnious oxid, and the whole is then liltered and washed,

20 ment of arsenical sulfuric acid obtained by burning arand thearsenious oxid is retained on the filter, while senical sulfur ores, and particularly arsenical pyritcs, the hydrochloricucid solution, (retaining the unprecipithe gaseous products being passed in the usual, or any tated arsenic), is returned to a vessel from which it is suitable manner into a tower, such as afllover tower, fed, to the vessel, Or to one of the vessels, in which, as through which the sulfuric acid fiowswith the arsenic aforesaid, the sulfuric acid lies above the liquid arse- 25 dissolved in it, but the invention is applicable to the nious chlorid, or into a vessel containing sulfuric acid treatment of arsenical sulfuric acid from whatever from any other source, and the hydrochloric acid gas, source obtained. 1 I which is liberated by contact with this sulfuric acid, is

We will describe with reference c mpanying conducted to the tower, or dc-ursenicating' vessel, in diagrams, the way in which the invention may be pracwhich arsenions chlorid is being formed from arscnical 30 tically carried out and apparatus adapted for carrying sulfuric acid as aforesaid, and thus the hydrochloric it out, Figure 1 being adiagramniatic elevation and Fig. acid is circulated and rc-nsed in the process, and, in ad 2a diagrammatical plan of such apparatus. dition, that arsenic which was dissolved in the hydro- According to this invention the arsenical sulfuric chloric acid is returned to the process to be recovered acid, as it flows from the Glover tower is (preferably as already described.

35 after first being brought into contact witha reducing Any liquidltiSt'llbHlH chlorid, over and above that agent, suchas charcoal, whereby the arsenic compounds which is required to rcdissolvo the arscnious oxid preare reduced to the arscnious state), brought, in any suitcipitatod in the scrubbing tower, is fl'(t'(l from selenium able de-arscnicating tower, or vessel and at a tcmperaby filtration after the addition of the requisite amount I ture lower than the boiling point of arsenious chlorid of water to retain the arsenic in solution and precipb 40 into contact with hydrochloric acid gas (preferably rate the selenium and is tin-n treated with a further dry). A suitable temperature is between 90 and quantity of water for the scpu ration of arscnioils oxid ccntigrade. If the temperature were appreciably beas before dcscriln-d, connection is made between low 9i)" Centigrade an emulsion would be formcd from the dwarscnicutiug tower and scrubbing tower to onwhich it would be diflicult to separate the arscuious able inert gases to escape from the dc-arsI-nicatiug 45 chlorid and if the temperature were much above 100 tower. 100

UNITED s'rArEs PATENT UFFIGEQ JULIUS RASCHEN, ARTHUR EDWARD WAEEING, AND JEFF HENRY SHORES, or LIVERPOOL, ALKALI COMPANY LIMITED, OF LIVERPOOL,

ENGLAND, ASSIGNORS TO. THE UNITED ENGLAND.

Specification of Letters Patent.

Application filed March 21,1906. Serial No. 307,179.

PURIFICATION: OF ARSENICAL SULFURIG ACID.

Iatented Au 20, 1907.

To all 'whom it may concern:

ccntigrado the arsenious chlorid formed would be volatilizcd. By the aforesaid operation arscnious chlorid is formed, and nearly the whole of this will separate as an oily liquid when the sulfuric acid, containing it, is

l rcprr some a (Hover tower from which the arscnical sulfuricacid pussrs into a box 2, which is preferably arranged so that only an amount of acid corrospoiuling to the amount made runs off for treatment according to run into a suitable vessel, or vessels. The sulfuric acid this invention, for which purpose the'box 2 may haye 10 which is in the vessel, or vessels, in which the arscnious chlorid deposits as an oily liquid, as aforesaid, is proforably drawn off and subjected to the action of air which removes practically the whole of the remainingmsonious chlorid not previously separated as oily arse-nious i ii I two outlets, one, it), approximately double thc size of i the other 4 l, the smaller one being the outlet for arson-f ical sulfuric acid to be treated according to this invention, and the larger one bcing the outlet for the acid to be returned l'or circulating purposes to the (lay Lussac tower in the ordinary Way. From the box 2, the arsenicalsnlfuric acid passes into a vessel 3, containing charcoal, by which the arsenic compounds in the suliuric acid are reduced to the arsenious'state, and the sulfuric acid containing the whole, or practically the whole of the arsenic in the arscnious state, passes. by the pipe 5, from the space l, into the distributer 6, and thence bythe distributing pipes 7, (bent so as to form liquid seals against the passage of gas), into the packed de arsenicating tower 8 through which it passes, preferably in the same direction as the hydrochloric acid gas entering by th pipe 14. The temperature in the tower 8 is below the boiling point of arsenious chlorid and is preferablybetween 90 and 100 centigrade and. if necessary, the acid can be cooled to such temperature before it passes into the said tower. The sulfuric acid now contaihing the arsenic in the form of arsenious chlorid, passes, by the, pipe 9, into the Yr 1 l0, thence into the vessel 13, add thence into the vessel 17, which vessels comlnunicate with each other by pipes as shown, the upper pipes 11 and 15 being for the passage of the sulfuric acid' and the lower pipes 12 and Ill being for the passage of the liquid arsenious chlorid which separates and deposits, as an oily liquid as aforesaid, beneath the sulfuric acid. The object of thus arranging 'the said vessels and communications is to insure separation of the. arsenious chlorid from the sulfuric acid and thus prevent the hydrochloric acid gas, which is dvolved in the vessel 13, as hercimiftcr described, from carrying away any of the liquid arsenions chlorid with it back to the tower 8.

From the lower part of the separating vesscl 17 the arsenious chlorid passes, by the pipe 18, or the pipe 42, ipto the vessel 19, or the vessel 43, each comnmniqating with a scrubbing tower 20, provided with an air escape ipipc 14 and packed with suitable material, such as infverted V tiles of glazed earthenware, down which wat er is passed, the said water being circulated (by a pump, for cx unple, as indicated at 45), through the pipe 21, until the solution is of'aalcnsity of, or about 20 Twaddle. The sulfuric acid passing off from the upper part of the sepzirating vessel 17, by the pipe still contains a small lunonnt of arsenious chlorid in solution and to recover this and complete the purification of the said acid, the said acid is passed into a blowing vessel 23, which contains devices by which the said acid is spread over a large surface and air is caused to pass in contact therewith. Such devices may consist of per foratcd plates with baffle plates above to prevent sulfuric acid from being mechanically carried forward. \ir is blown in, by any suitable means (such as a pump indicated at if?) at lho lowcr part of the vcsscl 23 by the pipe 21, the said air passing through the pcrl'orations in thc trays and carrying off with it the remaining arscnious chlorid which passes into the tower 120, by the pipe 25, where it is lrcafed with water as hcrcinln-fin'c dcscribci-l, the air escaping by the pipe 44. The purified sulfuric acid passes away for use, by the pipe 17 which is brought up to a level necessary to retain the required depth of liquid in the vessel 23. The solution flowing from the Lower 20- consists of hydrochloric acid containing dissolved and suspended arscnious oxid. This mixture flows into one, or other, of the vessels It), lit in which it. is trcatcdwith liquid arsenious chlorid from the vessel 17, in order to re dissolve the arscnious oxid which has been precipitated in the scrubbing tower 20, the two vessels 19, 43 being used alternately (the communicating pipes being arranged and provided with valves so as to enable the communications to be'reversed) one such vessel being used for circulating purposes while the contents of the other vessel are being treated for the precipitation of selenium. On the addition of a little water (approximately three volumes water to one volume arsenious chlorid) separation of selenium takes place and this selenium is removed by filtration through a filter in the box 26, .the clear liquor running into the vessel 27. To this clear liquor is added such a quantity of water that a liquor of a density of about 28 Twaddle is obtained whereby about per cent. of the arsenic is precipitated as arsenions oxid. The mixture is then passed from the vessel 27, onto the filtering medium in the vessel 28, and the arsenious oxid is retainedby and washed on this filter and is obtained in a purified state not requiring sublimation. 'lhe hydrochloric acid solution, still retaining the rest of the arsenic (about 30 per cent) is returned through the pipc 29, to the tank 30 (which may be done by a pump 48) from which it.is passed by the pipe 31, to the vessel 13, so that, by contact with the sulfuric acid above the arsenious chlorid therein, the said hydrochloric acid gas is liberated and passes, by the pipe 14, intdthe tower 8, for re-use in the process described. If desired the arsenical sulfuric acid can be run direct into the tower 8 instead of first passing through the charcoal, or other reducing agent.

. We claim as our invention 1. The process of purifying arsenical sulfuric acid and obtaining :n-senfc therefrom in the condition of liquid :irsi-nious chlorid. consisting in bringing arsenical sulfuric acid into contact with hydrochloric acid gas at a temperature from no" t. to 1::o" substantially as described.

2. The process of' nn'lfying arsenlcal sulfuric acid and obtaining arsenictherefrom in the condition of liquid nr enious chlorid, consisting in reducingthe arse ic compounds in the arsenical sulfuric acid to the arsenlons state and then hrin;.:-in,* the acid into contact with hydrochlorlc acid gas in a manner substantially as described at a temperature from llo to 1::o"

It. The process of pur I no :u'senfcal sulfuric acid and obtaining arsenic ther from. consisting in treating the arscnical sulfuric acid at a itilllltillilll'k from no t. to a point just below the boil ng; point of arsenious chlorid with lrvdrm'hloric acid gas in a manner substantially as de:

scribed and then treating the liquid arscnious ehlorldso" produ ed with a limited quantity of water. and filtering the solution so as to separate selenium and adding to the solution flitcrcd oft a further quantity of water and filterinc so as to separate arscnious oxid.

l. 'lhc a-ocessof purifying :li'scnicnl sulfuric acid and obtaining arsenic thcrcl'rom. consisting in reducing the urscnic compounds in the :irscnicnl sulfuric acid to tho. rsenions stale and then treating the acid. at a temperalur t'ronl Elf)" t'. to a point just below the boiling point of :irseninnschlorid. with lcvdrochloric acid gas in a manner substantially as described and treating the liquid arsonious chlorid so produced with a limited quantity of water, and filtering the solution so as to separate seloninm and adding to the solution filtered off a further quantity or water, and filtering so as to separate arscnlous oxid.

T. The process of pnrll' \in arsenlcal sullnrlc acld and obtaining arsenic therefrom consisting |n treating the arsenfcal sulfuric acid at a temperature from no" t, to a point just below the boiling point of ursenions chlorid with hydrochloric acid gas in a nmnncr substantially as descriheiL-nml allowing the liquid arson ions chlorid formed ti.-llto prots ot' purifying arsenioal sulfuric acid and ohtaiuiu; arsotit- 'theret'rom. consisting: in redut-iu r the arsouio compounds in tho arsouioal sulfuric acid to tho a st-uious stato and tltott troatiug tho arid at a tempera ture t't'otu 5H) t. to a point just ltolow tho hoiling point of ar utiotts t-hlorid with h \dr .ehlorio arid gas in a nanner suhstantialtr as dosorihotl and allowing tho liquid arsenious.ohlorid formed to soparato from the sult'urio acid, and troaliuy: tho liqttid arsonious ohlorid with a limited quantity of wator. attd troatiut, tho sult'ut'it' aoid with air and passing tlto 'os iut a wator soruhhor attd addingto tho atsonious o.\td so soparatod lquid arsonious ohlorid.

tho solutic-u thus tot-mod hoiug troatod with a lituitod quantity ot' wator, tltou tiltoriug tlto solution to soparato solouiulu anti adding. to tlto solution tiltorod oil a further quantity ol wator. and littering so as to soparato :it'souion; ttxid.

T. 'iho proooss ut' purit'ytt'ty: a souioal sult'urio aoid and ohlaiuiug' souio thorot'rout. l tt'oatit the arsouit-al sulluritarid at a totuporatur o t'rnut 5H) t, to a poittt just lielow tlto uoiliu: point of arsouious ohlorid witlt hydrot-htorio :toid gas in a utauuor substantially as dosrrihed and troatit tho liquid arsouious ltlorid so produt'ed with a iilltiloli uantity ot wator. and treating: tho sulturio acid with air and pit -sin: tho gases into a wator st'ruhhor and oil-tin; to tho arsouious oiid, so soparatod. liquid arseni- .|ts ol|lt,t-itl.,llt solution tltus t'orutod hoiug' troatod with a liutilod uantity ot l|l|', thou liltoriug tho solution so as to sopatato solouiutu. and adding to tho solution tiltored ttti'. a l'urthor quantity of wator, :tud liltot'iug so as to sopurato arsonious oxid. attd roturuing' tlto hydruchlot-lt" aoid so as to liltorato tho ]l \'(|l' t('|litl|i(' arid gas by moans ot' sullurit' :toid. thou routilizi 4' tlto lihoratod gas in the pro dttotiott of liquid arsouious ohlorid t't'utu t'urt'hor quautitios ot arsouit'al sull'urio arid.

H. 'iho proooss of purifying l sulturio arid and Attainingarsouitthorot'rout. oonst. lil;.' in roduoiur; tho a "tl'lo t-o'uqtttuud in tho arsouiteal sulfurio arid to tho .t'tttttlls stato and thou lroatitu: tho at'id at a tontporzrtut-o t'rout til)" (i to a point just hotow. tho hoilitu: point of arsouious ohtorid with hydroohtorio aoidfgas in u .utaunor substantially ts dost-rihod and treating tho liquid arsenious ohtor'ot so produt-od with a limitodquantity ot' wator. and lroattu: tho sult'uritzit-id with and passitu; tho sos into a wator-soruhhor and adding; to the atsonious oxith so soparatodf liquid arsouious ohlurld. tho solution thus t'ortnod hoit lroatod with a lituilod quantity of waltl'. thou tiltoriu; tho solution so as to soparato solouiunt. and adding to th sotutiou tiltorod oil. a t'urthor quantity ro-utilizing tho lihoratod gas in the production of liquid arsouious ohlot-id from further quantities of arseuical sulfuruid.

.t. The proooss ot purifying arsouiral sulfuric acid and ohtaiuin; arsonio thorot'rom. by treating the arseuicztl sult'tu'it: arid at a temperature from till t. to a point just itelow the hoilinL point of arsouious ohiorid. with hydrovhtoritarid ts in a mannotsuhstantially as described. and allowtto: tho liquid arsouious ohlorid formed to sep arato t'rotu the sult'ur'io aoitl. and treating tlte liquid arseniotts ohlorid with a lituitod quantity of wator. and troatiu; tho sult'uritavid with air. and p: in: tho gases into a wator-srruhltor and adding; to tho 2 onions oxid so soparatod. liauid onions t-hlorid. tho solution thus formed twin troatod with a litnitod quantity of wator. thou tilterin; the solution to s parato tho solouiutn and adding to the solution tiltorotl oft a t'urthor quantity of wator. and lill'illL' so as to soparato arsonious oxid and roturning tho hydrurhh l'it' aoid so as to lihorato tho hydrochloric acid s h moans ot' sult'uritaoid. atul thou utilizing th gas so lihoratod in tho produotiou ot liquid :trsouious ohlorid front further quautitios ot' arsonioal sultnrto aoid and returning the arsouious oxid which was di olved in the II VtIItN'IIIUl'iC arid to tho proooss l'or rorovoro It). 'tho process of purit lg arsouit-al sulfuric acid anti ohtaiuin arsonio thorot'rotn run. stin: itt reducing the at sonic ootupouuds iu the arsonital sult'urio acid to the a 'souious stato. thou troatiu: tho :toid at a totuporat'uro t'rotu fit) t. to a point just holow the boiling point of arsouions hlurid with h \'droohlorir gas in a manner sulr stanttally as dostt-ihod and allowing tho liquid arsonious ohlorid fortuotl to sopurato from tho sult'urio acid and treating tho liquid :lt'souious ohtorid with a litnitod quantity oi wator and troatinu; tho sult'ut'itarid with air and pa sitt tho gasos into a wator 'soruhhoiand adding to the arsoulous oxid. sooparatotl. liquid arsonious ohlorid, the

illitstillluli) whoroot' wo haro uod this spooitioatiou ltt tho prosouoo of two suhsorihin; wituos os. 

